Inception of anthropogenic activities and palaeoclimatic reconstruction during the Late Holocene from a high-altitude region, Western Himalaya, India: Palynological perspective

Abstract

Palynological analyses of surface soil and sub-surface sediments were undertaken from Chopta-Tungnath, Uttarakhand State, India, to decipher the Late Holocene climatic changes, along with the inception, intensification and impact of anthropogenic activities in this high-altitude Himalayan region. The study area is characterised by mixed-temperate forests and alpine meadows. The development of modern palynological analogues has been done by the surface soil samples that were collected along an altitudinal transect (2700–3680 m), encompassing three distinct vegetation zones: mixed-temperate forests, tree-line vegetation, and alpine-scrub and meadows. The modern analogues were primarily generated to interpret the pollen-vegetation relationship and are compatible with the sub-surface fossil pollen records. Sub-surface sampling was done from a trial trench (105 cm), dug in the zone of mixed-temperate forests. Based on the radiocarbon dates (¹⁴C), climate fluctuations over the last 5070 years have been inferred through variations in the ratio of arboreal to non-arboreal pollen (AP/NAP), along with the subtle variations in the frequencies of temperate broad-leaved taxa. Besides, deducing the Late Holocene climatic changes, the palynological assemblages were also used to record the anthropogenic activities in the region. Around 850 yr BP, the evidence of human impact is manifested by the declining trend in the pollen frequencies of Quercus and Rhododendron, which indicate the degradation of these two arboreal components of the forest. There is a corresponding spike of Asteroideae, Cichorioideae and ruderal pollen, which are related to human activities. The increasing frequencies of coprophilous (dung-loving) fungi in the palynological assemblages of the sub-surface sediments, around 900 yr BP, provide further evidence towards the introduction of grazers in the area.